Within certain limits, the amount of light absorbed can be linearly correlated to the concentration of analyte present.
The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels.
Applying the Beer-Lambert law directly in AA spectroscopy is difficult due to variations in the atomization efficiency from the sample matrix, and nonuniformity of concentration and path length of analyte atoms (in graphite furnace AA).
The main advantages of the graphite furnace comparing to aspiration atomic absorption are the following: GFAA spectrometry instruments have the following basic features: 1. a source of light (lamp) that emits resonance line radiation; 2. an atomization chamber (graphite tube) in which the sample is vaporized; 3. a monochromator for selecting only one of the characteristic wavelengths (visible or ultraviolet) of the element of interest; 4. a detector, generally a photomultiplier tube (light detectors that are useful in low-intensity applications), that measures the amount of absorption; 5. a signal processor-computer system (strip chart recorder, digital display, meter, or printer).
GFAAs are more sensitive than flame atomic absorption spectrometers, and have a smaller dynamic range.